This invention relates to monitoring systems, and more particularly, to a system and a method that detects motor faults.
Automobiles are steered by a system of gears and linkages that transmit the turning motion of the steering wheel to the front wheels. As automobile designs shift weight to the front wheels to improve riding comfort and vehicle handling, more effort is needed to turn the front wheels and provide sufficient torque to overcome the drag that exists between the front wheels and the road.
Power steering systems are designed to reduce steering effort and improve maneuverability. Some vehicles use engine driven hydraulics to amplify the torque applied by the steering wheel to the front wheels. A mechanically-driven or an electrically-driven pump maintains a hydraulic fluid, such as oil, under pressure. The rotation of the steering wheel actuates a valve, which supplies or drains fluid to a power cylinder, which reduces the steering effort needed to turn the wheels.
Some vehicles mechanically couple an electric motor to the steering shaft through steering gears. Variable torque assist levels can be realized when speed sensitive controllers alter the required torque to maneuver a vehicle based on vehicle speed. By maintaining a threshold torque that must be overcome to turn the wheels, the system impedes the front wheels from turning when a driver inadvertently tugs the steering wheel because of rough road conditions, a flat tire, or other mechanical failures.
The power steering systems described above aide the steering of automobiles at high and low speeds. However, under some circumstances, when a motor fails, the driver must overcome the additional torque of the motor failure, and if hydraulics are used, steer the fluid that couples the steering wheel to the front wheels. This may happen, for example, when a motor shorts, a motor circuit opens, or other motor faults occur. The present invention is directed to a system and a method that detects a motor failure so that the motor can be separated from the steering system when a fault occurs.